Capacity Variable Type Rotary Compressor and Driving Method Thereof and Driving Method for Air Conditioner Having the Same

ABSTRACT

In a capacity variable type rotary compressor, its operation method and an operation method of an air conditioner having the same, a plurality of discharge holes are formed, and one of the discharge holes is connected to a bypass hole, which is opened and closed by a sliding valve according to a pressure difference, so as to be selectively connected to an intake hole. Accordingly, a cooling capability lowering rate is increased during capacity varying operation of the compressor, such that the air conditioner can be variously controlled, and unnecessary power consumption of the compressor and the air conditioner having the same can be reduced. 
     Also, by using a pilot valve which is economical and reliable, back pressure of the sliding valve can be speedily and accurately switched. Accordingly, the capacity variable device in accordance with the present invention can be widely used for a compressor or an air conditioner that should perform frequent cooling capability control, and efficiency degradation thereof can be prevented from occurring.

TECHNICAL FIELD

The present invention relates to a capacity variable type rotary compressor, and particularly, to a capacity variable type rotary compressor, an operation method thereof and an operation method for an air conditioner having the same capable of controlling cooling capability by discharging a refrigerant gas of a compression chamber accordingly.

BACKGROUND ART

In general, a rotary compressor is used for an air conditioner. As functions of the air conditioner are diversified, a rotary compressor that can vary its capacity is being required.

As techniques for varying the capacity of the rotary compressor, the so called an inverter method of controlling the revolutions of the compressor by employing an inverter motor has been well known. However, this technique is problematic for the following reasons. First, the inverter motor itself is expensive, which causes an increase in unit cost. Also, even though most air conditioners are used as cooling devices, improving cooling capability under cool circumstances is more difficult than improving the cooling capability under warm circumstances.

For this reason, instead of the inverter method, “a technique of varying the capability of compressing a refrigerant by capacity exclusion switching” (an idling or compressing conversion technique) is being widely used, in which a portion of a refrigerant gas being compressed in a cylinder is directed out of the cylinder to vary the capacity of the compression chamber.

However, because refrigerant bypasses through the valve, most capacity variable compressors employing the idling or compression conversion technique have the disadvantage of the high resistance of bypass circuit. Therefore, a cooling capability lowering rate in capacity exclusion operation is only 80˜85% of the cooling capability lowering rate in capacity filled operation.

Also, because those compressors cannot speedily switch their operation modes, there is a limit in using them for compressors or air conditioners that require frequent cooling capability control.

DISCLOSURE OF THE INVENTION

Therefore, it is an object of the present invention to provide a capacity variable type rotary compressor, its operation method and an operation method of an air conditioner having the same capable of allowing various control on operation of an air conditioner and preventing unnecessary power consumption by increasing a cooling capability lowering rate during capacity exclusion operation.

It is another object of the present invention to provide a capacity variable type rotary compressor, its operation method and an operation method of an air conditioner having the same, whereby the capacity variable type rotary compressor can speedily convert its operation mode such that it can be used for a compressor or an air conditioner which should perform frequent cooling capability control.

To achieve the above object, there is provided a capacity variable type rotary compressor comprising: a casing that is provided with a gas intake pipe communicating with an evaporator and a gas discharge pipe communicating with a condenser; a cylinder that is fixedly installed in the casing, and includes an internal space at its center in which a rolling piston compresses a refrigerant while orbiting, an intake hole penetratingly formed at the internal space in a radial direction and communicating with the gas intake pipe, and a vane slit formed in a radial direction so as to support a vane contacting with the rolling piston in a radial direction and dividing the internal space into a compression chamber and an intake chamber; a plurality of bearing plates that form an internal space together by covering both upper and lower sides of the cylinder, discharge holes formed on the same axis, communicating with the internal space of the cylinder and discharging a compression refrigerant, and a bypass hole communicating with one discharge hole and communicating with the intake hole of the cylinder; a plurality of discharge valves that are installed at a front end surface of each discharge hole so as to open and close the discharge hole of each bearing plate; a capacity varying unit that is coupled to the bearing plate and selectively opens and closes the bypass hole of the bearing plate to exclude a portion of a compression refrigerant to the intake hole; and a back pressure switching unit that differentially supplies back pressure to the capacity varying unit so as to allow the. capacity varying unit to open and close the bypass hole according to an operation mode of the compressor.

To achieve the above object, there is provided a capacity variable type rotary compressor comprising: a casing that is provided with a gas intake pipe communicating with an evaporator and a gas discharge pipe communicating with a condenser; a cylinder that is fixedly installed in the casing, and includes an internal space at its center in which a rolling piston compresses a refrigerant while orbiting, an intake hole penetratingly formed at the internal space in a radial direction and communicating with the gas intake pipe, and a vane slit formed in a radial direction so as to support a vane contacting with the rolling piston in a radial direction and dividing the internal space into a compression chamber and an intake chamber; a plurality of bearing plates that form an internal space together by covering both upper and lower sides of the cylinder, discharge holes formed on different axes, communicating with the internal space of the cylinder and discharging a compression refrigerant, and a bypass hole communicating with one discharge hole and communicating with the intake hole of the cylinder; a plurality of discharge valves that are installed at a front end surface of each discharge hole so as to open and close the discharge hole of each bearing plate; a capacity varying unit that is coupled to the bearing plate and selectively opens and closes the bypass hole of the bearing plate to exclude a portion of a compression refrigerant to the intake hole; and a back pressure switching unit that differentially supplies back pressure to the capacity varying unit so as to allow the capacity varying unit to open and close the bypass hole according to an operation mode of the compressor.

To achieve the above object, there is provided an operation method of a capacity variable type rotary compressor of claim 1 or 3, alternately performing: a power operation mode in which the operation is performed with the maximum cooling capability, as a capacity varying unit blocks a bypass hole when the compressor is started; and a saving operation mode in which, during the power operation mode, if the cooling capability needs to be lowered upon calculating the proper cooling capability of the compressor by a control unit, the back pressure switching unit is operated such that the capacity varying unit opens the bypass hole to allow all of the compression refrigerant within a cylinder to be excluded to an intake hole.

To achieve the above object, there is provided an operation method of a capacity variable type rotary compressor of claim 2 or 4, alternately performing: a middle operation mode in which a capacity varying unit opens a bypass hole when the compressor is started so as to allow a portion of a compression refrigerant of a cylinder to be excluded to an intake hole; a power operation mode in which the operation is performed with the maximum cooling capability as the capacity varying unit blocks the bypass hole upon operating a back pressure switching unit after the middle operation mode is performed for a certain period of time; and a middle operation mode in which, during the power operation mode, if the cooling capability needs to be lowered upon calculating the proper cooling capability of the compressor by a control unit, the back pressure switching unit is operated in the opposite manner such that the capacity varying unit opens the bypass hole to allow a portion of the compression refrigerant of the cylinder to be excluded to the intake hole.

To achieve the above object, there is provided an operation method of an air conditioner having a capacity variable type rotary compressor of claims 1 and 3, performing: a maximum cooling capability mode in which, if an indoor temperature is higher than a set temperature (A) upon comparing the indoor temperature to the set temperature (A) with power supplied, the operation is performed with the maximum cooling capability as a capacity varying unit of a compressor blocks a bypass hole communicating with an indoor space of a cylinder; a minimum cooling capability mode in which, during the maximum cooling capability mode, if the indoor temperature is lower than the set temperature (A) upon comparing the indoor temperature with the set temperature (A), the capacity varying unit opens the bypass hole to allow all of the compression refrigerant of the internal space of the cylinder to be excluded to an intake hole, wherein if the indoor temperature is higher than the set temperature (A), the maximum cooling capability mode is continuously performed; and a stopping mode in which, during the minimum cooling capability mode, if the indoor temperature is lower then a set temperature (B) upon comparing the indoor temperature with the set temperature (B), the compressor is stopped by turning OFF power.

To achieve the above object, there is provided an operation method of an air conditioner having a capacity variable type rotary compressor of claims 1 and 3 or 2 and 4, performing: a middle cooling capability mode in which, if an indoor temperature is higher than a set temperature (A) upon. comparing the indoor temperature with the set temperature (A) with power supplied, a capacity varying unit of a compressor opens a bypass hole communicating with an internal space of a cylinder to allow a portion of a compression refrigerant within a cylinder to be excluded to an intake hole; a maximum cooling capability mode in which, during the middle cooling capability mode, if the indoor temperature is higher than the set temperature (A) upon comparing the indoor temperature with the set temperature (A), the operation is performed with the maximum cooling capability as the capacity varying unit blocks the bypass hole communicating with the internal space of the cylinder; a middle cooling capability mode in which, during the maximum cooling capability mode, if the indoor temperature is lower than the set temperature (A) upon comparing the indoor temperature with the set temperature (A), the bypass hole is opened to allow a portion of a compression gas to be excluded; and a stopping mode in which, during the middle cooling capability mode, if the indoor temperature is lower than a set temperature (B) upon comparing the indoor temperature with the set temperature (B), the compressor is stopped by turning OFF the power.

EFFECT

In a capacity variable type rotary compressor, its operation method and an operation method of an air conditioner having the same, a plurality of discharge holes are formed, and one of the discharge holes is connected to a bypass hole, which is opened and closed by a sliding valve according to a pressure difference, so as to be selectively connected to an intake hole. Accordingly, a cooling capability lowering rate is increased during capacity varying operation of the compressor, such that the air conditioner can be variously controlled, and unnecessary power consumption of the compressor and the air conditioner having the same can be reduced.

Also, by using a pilot valve which is economical and reliable, back pressure of the sliding valve can be speedily and accurately switched. Accordingly, the capacity variable device in accordance with the present invention can be widely used for a compressor or an air conditioner that should perform frequent cooling capability control, and efficiency degradation thereof can be prevented from occurring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram that illustrates an air conditioner provided with a capacity variable rotary compressor in accordance with one embodiment of the present invention;

FIG. 2 is a sectional view taken along line II-II of FIG. 3 to illustrate one example of the capacity variable type rotary compressor in accordance with one embodiment of the present invention;

FIG. 3 is a sectional view taken along line I-I of FIG. 2;

FIG. 4 is a view that illustrates a power operation process of the capacity variable type rotary compressor in accordance with one embodiment of the present invention;

FIG. 5 is a view that illustrates a saving operation process of the capacity variable type rotary compressor in accordance with one embodiment of the present invention;

FIGS. 6 and 7 are a schematic view and a flow chart that illustrate an operation aspect of an air conditioner having the capacity variable type rotary compressor in accordance with one embodiment of the present invention;

FIG. 8 is a sectional view taken along line I-I of FIG. 2 to illustrate the capacity variable type rotary compressor in accordance with another embodiment of the present invention;

FIG. 9 is a view that illustrates a power operation process of the capacity variable type rotary compressor in accordance with another embodiment of the present invention;

FIG. 10 is a view that illustrates a middle operation process of the capacity variable type rotary compressor in accordance with another embodiment of the present invention;

FIGS. 11 and 12 are a schematic view and a flow chart that illustrate an operation aspect of the air conditioner having the capacity variable type rotary compressor in accordance with another embodiment of the present invention; and

FIG. 13 is a sectional view that illustrates a modified example of a bypass hole of the capacity variable type rotary compressor in accordance with the present invention.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

Hereinafter, a capacity variable type rotary compressor, its driving method and a driving method of an air conditioner having the same in accordance with one embodiment of the present invention will now be described in detail.

FIG. 1 is a block diagram that illustrates an air conditioner provided with a capacity variable rotary compressor in accordance with one embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II of Figure to illustrate one example of the capacity variable type rotary compressor in accordance with one embodiment of the present invention, FIG. 3 is a sectional view taken along line I-I of FIG. 2, FIG. 4 is a view that illustrates a power operation process of the capacity variable type rotary compressor in accordance with one embodiment of the present invention, FIG. 5 is a view that illustrates a saving operation process of the capacity variable type rotary compressor in accordance with one embodiment of the present invention, FIGS. 6 and 7 are a schematic view and a flow chart that illustrate an operation aspect of an air conditioner having the capacity variable type rotary compressor in accordance with one embodiment of the present invention, FIG. 8 is a sectional view taken along line I-I of FIG. 2 to illustrate the capacity variable type rotary compressor in accordance with another embodiment of the present invention, FIG. 9 is a view that illustrates a middle operation process of the capacity variable type rotary compressor in accordance with another embodiment of the present invention, FIG. is a view that illustrates the middle operation process of the capacity variable type rotary compressor in accordance with another embodiment of the present invention, and FIGS. 11 and 12 are a schematic view and a flow chart that illustrate an operation aspect of the air conditioner having the capacity variable type rotary compressor in accordance with another embodiment of the present invention.

As shown in FIGS. 1 to 3, the rotary compressor in accordance with the present invention includes a casing 1 to which a gas intake pipe (SP) and a gas discharge pipe (DP) are communicably installed, a motor unit installed at an upper side of the casing 1 and generating a rotating force, and a compression unit installed at a lower side of the casing and compressing a refrigerant by a rotating force generated by the motor unit.

The motor unit includes a stator (Ms) fixed inside the casing 1 and receiving power from the outside and a rotor (Mr) disposed in the stator (Ms) with a certain gap therebetween and rotating, interworking with the stator (Ms).

The compression unit includes a cylinder 10 having an annular shape and installed inside the casing 1, a main bearing plate (main bearing) 20 and a sub-bearing plate (sub-bearing) 30 covering both upper and lower sides of the cylinder and forming an internal space (V) together, a rotary shaft 40 pressingly inserted in the rotor (Mr), supported at the main bearing 20 and the sub-bearing 30 and transferring a rotating force, a rolling piston 50 rotatably coupled to an eccentric portion 41 of the rotary shaft 40 and compressing a refrigerant while orbiting within the internal space of the cylinder 10, a vane 60 coupled to the cylinder 10 movably in a radial direction to pressingly contact with an outer circumferential surface of the rolling piston 50 and dividing the internal space (V) of the cylinder 10 into an intake chamber and a compression chamber, and a first discharge valve 71 and a second discharge valve 72 openably and closably coupled to front ends of a first discharge hole 2 and a second discharge hole 32 that are provided at the main bearing 20 and the sub-bearing 30, respectively.

Also, the compression unit further includes a capacity varying unit 80 provided at one side of the sub-bearing 10 and varying a capacity of the compression chamber, and a back pressure switching unit connected to the capacity varying unit 80 and operating the capacity varying unit 80 by a pressure difference according to an operation mode of the compressor.

As shown in FIGS. 1 to 3, the cylinder 10 is formed as an annular shape to allow the rolling piston 50 to make a relative movement, and includes a vane slit 11 linearly formed at its one side so as to allow the vane 60 to linearly move in a radial direction, an intake hole 12 penetratingly formed at one side of the vane slit 11 in a radial direction and communicating with the gas intake pipe (SP), a first gas guiding groove 13 a and a second guiding grove 13 b formed at the other side of the vane slit 11 and communicating with the first discharge hole 22 and the second discharge hole 32 of the main bearing 20 and the sub-bearing 30 so as to induce discharge .of a refrigerant gas, and a communication hole 14 penetratingly formed under the intake hole 12 in an axial direction and communicating with the intake hole 12 so as to introduce a refrigerant, which has passed through the bypass hole 13, to the internal space (V) of the cylinder 10.

The main bearing 20 is formed as a disc shape having at its center a bearing hole 22 supporting the rotary shaft 40 in a radial direction. As for the main bearing 20, a first discharge hole 22 is formed at one side of the cylinder 10, namely, at a portion of the main bearing 20 spaced apart from the vane slit 11 at a distance as long as about 345 degrees, the maximum pressure angle, in a direction that the rolling piston 50 rotates. A first muffler 23 having a resonant chamber is fixedly installed on an upper surface of the main bearing 20 so as to receive the first discharge hole 22.

The sub-bearing 30 is formed as a disc shape having at its center a bearing hole 32 supporting the rotary shaft 40 in a radial direction. As for the sub-bearing 30, a second discharge hole 32 is formed at one side of the vane slit 11 of the cylinder 10, namely, at a portion of the sub bearing 30 spaced apart from the vane slit 11 at a distance as long as about 345 degrees, the maximum pressure angle, in a direction that the rolling piston 50 rotates, and a second muffler 33 having a resonant chamber to receive the second discharge hole 32 and the communication hole 14 of the cylinder 10 is fixedly installed at a lower surface of the sub-bearing 30. Here, preferably, a gas flow path (used together with a bypass hole) is formed to a particular depth to connect the second discharge hole 32 with the communication hole 14 of the cylinder 10 and to form a bypass hole 34 together with the second muffler 33.

As shown in FIG. 3, the second discharge hole 32 may be formed colinearly with the first discharge hole 22, namely, aligning with the first discharge hole 22 in an axial direction. However, as occasion demands, as shown in FIG. 8 the second discharge hole 32 is preferably formed at a position where cylinder pressure of its inlet end becomes lower than the pressure within the casing 1, within a range of about 170˜200 degrees (more particularly 180˜190 degrees) from the vane slit 11 in a direction of the inlet hole 12 (i.e., in a direction that the rolling piston rotates), such that the cooling capability during the saving operation mode can be varied up to 50%.

The second discharge hole 32 may have the same diameter as that of the first discharge hole 22. As occasion demands, the diameter of the second discharge hole 32 is preferably greater than that the first discharge hole 22, such that the second discharge valve 71 may be easily opened.

Also, a valve hole 35 in which the sliding valve 81 of the capacity varying unit 80 is slidingly inserted is formed at one side of the sub-bearing 30, namely, at a position perpendicular to the inlet hole 12 of the cylinder 10 in a direction crossing the inlet hole 12 in the view of plane-projection.

The valve hole 35 is formed by being recessed like a groove in an outer circumferential surface of one side of the sub bearing 30 such that its side surface is formed as a wall surface so as to support one end of a valve spring 82 to be described later or support a rear surface of a first pressure portion 81 a of the sliding valve 81, and its front surface is opened, in which a valve stopper 83 is pressingly inserted so as to support a second pressure portion 81 b of the sliding valve 81 to be described later. Here, a first back pressure hole 35 a and a second back pressure hole 83 a are respectively formed at a central portion of the wall surface of the valve hole 35 and a central portion of the valve stopper 83, and are respectively connected to a first connection pipe 92 and a second connection pipe 93 of a back pressure switching unit (to be described later) to supply a high or low-pressure atmosphere to the sliding valve 81.

The first discharge valve 71 and the second discharge valve 72 may have the same elasticity coefficient. However, as occasion demands, preferably, the elasticity efficient of the second discharge valve 72 is smaller than that of the first discharge valve 71, such that the second discharge valve 72 can be easily opened and a compression refrigerant can be speediy bypassed.

As shown in FIGS. 2 to 5, the capacity varying unit 80 includes a sliding valve 81 slidingly inserted in the valve hole 35 and opening and closing the bypass hole 34 while moving within the valve hole 35 according to a pressure difference due to the back pressure switching unit, at least one valve spring 82 elastically supporting a moving direction of the sliding valve 81 and allowing the sliding valve 81 to move in a closed position when there is no pressure difference between both ends, and a valve stopper 83 shielding the valve hole 35 to prevent separation of the sliding valve 82.

The sliding valve 81 includes a first pressure portion 81 a formed to slidingly contact with an inner circumferential surface of the valve hole 35, placed toward the wall surface of the valve hole 35 and opening and closing the bypass hole 35 upon receiving pressure from the back pressure switching unit, a second pressure portion 81 b formed to slidingly contact with the inner circumferential surface of the valve hole 35, placed toward the valve stopper 83 and receiving pressure from the back pressure switching unit and a communication portion 81 c connecting the two pressure portions 81 a and 81 b and having a gas passing path formed between its outer circumferential surface and the valve hole 35 and communicating with the bypass hole 34.

The first pressure portion 81 a is longer than a diameter of the bypass hole 34, and a spring fixing groove 81 d to which the valve spring 82 is insertedly fixed is formed inwardly from the rear end of the first pressure portion 8, so that the length of the valve can be minimized.

The back pressure switching unit includes a pressure switching valve assembly 91 communicating with the gas intake pipe (SP) and the gas discharge pipe (DP) and formed to alternately connect the gas intake pipe (SP) and the gas discharge pipe (DP) to both sides of the capacity varying unit 80, a first connection pipe 92 connecting a first outlet 94 c of the pressure switching valve assembly 91 to the first pressure portion 81 a, and a second connection pipe 93 connecting a second outlet 94 d of the pressure switching valve assembly 91 to the second pressure portion 81 b of the capacity varying unit 80.

The switching valve assembly 91 includes: a switching valve housing 94 having a low-pressure side inlet 94 a connected with the gas intake pipe (SP), a high-pressure side inlet 94 b connected to the gas discharge pipe (DP), a first outlet 94 c connected to the first connection pipe 92, and a second outlet 94 d connected to the second connection pipe 93; a switching valve 95 slidingly coupled to the inside of the switching valve housing 94 and selectively allowing connection between the low-pressure side inlet 94 a and the first outlet 94 c and between the high-pressure side inlet 94 b and the second outlet 94 d or between the low-pressure side inlet 94 a and the second outlet 94 d and between the high-pressure side inlet 94 d and the first outlet 94 c; an electromagnet 96 installed at one side of the switching valve housing 94 and moving the switching valve 95 by applied power; and a switching valve spring 97 including a compression spring for restoring the switching valve 95 when the power being applied to the electromagnet 96 is cut off.

Preferably, the electromagnet 96 is possibly small and achieves small power consumption of approximately 15 Watt/Hour or less, thereby improving reliability and reducing a cost and power consumption.

In the drawing, undescribed reference numeral 2 is a condenser, 3 is an expansion mechanism, 4 is an evaporator, 5 is an accumulator, 6 is a condenser blower fan, 113 is a valve stopper and 114 is a plug.

The operation and effect of the capacity variable type rotary compressor in accordance with the present invention will now be described. Namely, when power is applied to the motor unit, the rotary shaft 40 rotates, and the rolling piston 50 orbits within the internal space (V) of the cylinder 10, forming a volume with the vane 60, such that a refrigerant gas is taken in, compressed and discharged to the casing 1. The refrigerant gas is discharged to the condenser 2 of a cooling cycle device, passes through the expansion mechanism 3 and the evaporator in order, and then is re-taken into the internal space (V) of the cylinder 10 through the gas intake pipe (SP). Such a series of processes are repetitively performed.

Here, the capacity variable type compressor is operated in a saving operation mode or a power operation mode according to an operation state of an air conditioner employing the same. The operation will now be described in more detail. As shown in FIG. 4, during the power operation mode, by applying power to the electromagnet 96 of the back pressure switching unit which is a pilot valve, the switching valve 95 moves by overcoming an elastic force of the switching valve spring 97 to allow the high-pressure side inlet 94 a to be in communication with the first connection pipe 92 and also to allow the low-pressure side inlet 94 b to be in communication with the second connection pipe 93. Thusly, the high-pressure refrigerant gas discharged through the gas discharge pipe (DP) is introduced toward the first compression portion 81 a of the sliding valve 81 through the first connection pipe 92 while the low-pressure refrigerant gas taken into the gas intake pipe (SP) is introduced toward the second pressure portion 81 b of the sliding valve 81 through the second connection pipe 93, such that the sliding valve 81 moves toward the second pressure portion 81 b to allow the first pressure portion 81 a to block the bypass hole 32. Here, a compression gas being compressed within the internal space (V) of the cylinder 10 overcomes the first discharge valve 81 and the second discharge valve 75, passes through the first discharge hole 22 and the second discharge hole 32 and is discharged to the first muffler 23 and the second muffler 33. Here, as the sliding valve 81 blocks the bypass hole 34, the compression gas discharged to the second muffler 33 is temporarily discharged only at an initial driving stage and is not discharged any further. In the end, every compression gas is discharged into the casing 1 through the first discharge hole 22 and is moved to the condenser 2. Seeing that the pressure of the first connection pipe 92 and the pressure of the second connection pipe 93 are balanced when the compressor is started, such operation can implement the power operation mode in such a manner that the first pressure portion 81 a of the sliding valve 81 blocks the bypass hole 34 only with an elastic force of the valve spring 82 without separately operating the back pressure switching unit.

Then, as shown in FIG. 5, during the saving operation mode, by cutting off power being applied to the electromagnet 96 of the back pressure switching unit, which is a pilot valve, the switching valve 95 moves by a restoration force of the switching valve spring 97 to allow the high-pressure side inlet 94 a to be in communication with the second connection pipe 93 and also allow the low-pressure side inlet 94 b to be in communication with the first connection pipe 92. Thusly, a high-pressure refrigerant gas discharged through the gas discharge pipe (DP) is introduced toward the second pressure portion 81 b of the sliding valve 81 through the second connection pipe 93 while a low-pressure refrigerant gas taken in through the gas intake pipe (SP) is introduced toward the first pressure portion 81 a of the sliding valve 81, such that the sliding valve 81 moves toward the first pressure portion 81 a by overcoming an elastic force of the valve spring 82 and the bypass hole 34 meets the communication portion 81 c of the sliding valve 81 to be opened. Here, because a compression gas being discharged to the second muffler 33 passes through the bypass hole 34 and is introduced to the intake hole 12, the second muffler 33 is in a relatively low pressure state as compared to the first muffler 23. Thusly, the refrigerant gas discharged from the cylinder 10 is discharged only toward the second discharge hole 32 in a relatively low pressure state, such that the compressor rarely performs compression.

The rotary compressor having the capacity variable device in accordance with the present invention is operated in the manner illustrated in FIG. 7. Namely, the operation is performed in the power operation mode achieving the maximum cooling capability in a state that the sliding valve 81 of the capacity variable unit 80 blocks the bypass hole 34 of the sub-bearing 30.

Then, a control unit calculates the proper cooling capability of the compressor in the power operation mode. If the cooling capability needs to be lowered, the back pressure switching unit is operated to thereby supply a high-pressure refrigerant gas to the high-pressure side inlet 94 a and the first connection pipe 92 and to supply a low-pressure refrigerant gas to the low-pressure side inlet 94 b and the second connection pipe 93, so that the saving operation mode is performed. Here, in the saving operation mode, the sliding valve 81 of the capacity varying unit 80 opens the bypass hole 34 and all of the compression refrigerant of the cylinder 10 is excluded to the intake hole 12. Here, if the saving operation is continued for a long time (commonly, longer than one minute), the pressure difference of the system no longer exists, and the intentional power operation upon switching the sliding valve 81 becomes impossible. Namely, because even the minimum pressure difference does not exist between the high-pressure side and the low-pressure side, switching to the power operation mode from the saving operation mode cannot be performed. For this reason, preferably, the maximum saving-operation time limit is set according to operational conditions, temperatures of the condenser 2 and the evaporator 4 or a temperature difference therebetween, or by a method of detecting high and low pressure. Here, the most economical method is setting the time limit by using the temperatures of the condenser 2 and the evaporator and the temperature difference therebetween.

As shown in FIG. 8, the air conditioner having the capacity variable type rotary compressor in accordance with the present invention can be operated as illustrated in FIG. 8. First, as power is applied, an indoor temperature is compared to a set temperature (A), and the maximum cooling capability operation (power operation) implementing the maximum cooling capability of the compressor is performed. Namely, the indoor temperature is detected and then is compared with the set temperature (A). If the indoor temperature is higher than the set temperature (A), the operation of the compressor is performed in a state that the back pressure switching unit is controlled to allow the capacity varying unit 80 to block the bypass hole 34. Here, before starting is performed with the maximum cooling capability, the indoor temperature is compared with the set temperature (A), and the required total cooling capability of the compressor is determined according to the temperature difference, so that the operation is performed according to the determined cooling capability. Accordingly, the cooling capability of the air conditioner can be variously controlled, the efficiency of the air conditioner is improved, and unnecessary power consumption can be prevented.

Then, during the maximum cooling capability operation, the indoor temperature is compared with the set temperature (A). If the indoor temperature is higher than the set temperature (A), the maximum cooling capability operation is continued. In contrast, if the indoor temperature is lower than the set temperature (A), the back pressure switching unit is controlled to allow the capacity varying unit 80 to open the bypass hole 34, and all of the refrigerant gas being compressed within the cylinder 10 is thusly excluded to the intake hole 12, thereby implementing the minimum cooling capability operation mode (saving operation) in which the cooling capability of the compressor becomes zero. Here, in case of the air conditioner, the cooling capability is controlled upon feeding back the indoor temperature for a relative short period of time (e.g., for three minutes). Normally, if the minimum cooling capability operation is performed longer than one minute, the pressure difference of a system is disappeared, which makes it impossible to intentionally convert the operation mode to the maximum cooling capability operation mode upon switching the sliding valve 81 of the compressor. Therefore, as in the operation method of the compressor, preferably, the maximum cooling capability operation time limit is set according to operational conditions, temperatures of the condenser and the evaporator or a temperature difference therebetween or by a method of detecting the high and low pressure. Preferably, the saving operation of the compressor, the minimum cooling capability operation, is performed for a period of time corresponding to 30˜40% of the power operation time so as to generate the required minimum pressure difference.

For example, because the cooling capability of the rotary compressor having the capacity varying device in accordance with the present embodiment is zero in the saving operation mode, if the total cooling capability is intended to be 40%, for three minutes, the power operation is performed for a period of time as long as 0.4*time (t) and the saving operation is performed for a period of time as long as 0.4*time (t). Here, because the saving operation cannot be performed longer than one minute, the power operation is performed for 0.4 minutes and the saving operation is performed for one minute, such that a series of operation modes for controlling the capacity of the compressor are frequently converted to optimize the operation of the air conditioner. Power consumption may be minimized by stopping the compressor during the saving operation.

Another embodiment of the present invention will now be described. Namely, in the aforementioned one embodiment, a plurality of discharge holes 22 and 32 are disposed on the same axis, and the operation of the compressor is divided into two modes of a power operation mode (cooling capability;100% operation) and a saving operation mode (cooling capability;0% operation). Also, the operation of the air conditioner applying the same is also divided into a maximum cooling capability operation (power operation of compressor) and a minimum cooling capability operation (saving operation of compressor). Also, the operation time of the maximum cooling capability operation and the operation time of the minimum cooling capability operation are controlled upon comparing an indoor temperature with a set temperature, thereby obtaining the optimum air-conditioning effect. In the present embodiment, however, as shown in FIG. 8, the first discharge hole 22 and the second discharge hole 32 are formed at a predetermined interval therebetween on different axes. In such a case, the power operation mode in which the operation is performed with the bypass hole 33 closed, is similar to that in the case where the two discharge holes are aligned on the same axis. However, if the bypass hole is opened, a portion of a refrigerant gas is excluded through the second discharge hole 32, and the remaining refrigerant gas is still moved toward the first discharge hole 22 by the rolling piston 50 so as to be further compressed and discharged. Therefore, the compressor is operated with the capacity of approximately 50% of the maximum operation (i.e., power operation mode). Accordingly, the compressor structure can be minimized and the capacity of the compressor can be lowered by approximately 50%, which allows various operation modes to be performed and improves the efficiency of the compressor.

If the plurality of discharge holes are disposed on different axes as mentioned above, the operation of the compressor can be performed in a middle operation mode which can lower a starting load. For example, as shown in FIG. 9, the valve spring 82 supporting the sliding valve 81 is disposed at a rear surface of the second compression portion 81 b. When the pressure of the: high-pressure side and the pressure of the low-pressure side are balanced at the time of stopping of the compressor, the sliding valve 81 moves toward the right side of the drawing by an elastic force of the valve spring 82; such that the communication portion 81 c of the sliding valve 81 overlaps with the bypass hole 34. If the compressor is started in such a state, a portion of a compression refrigerant is leaked to the bypass hole 34 through the second discharge hole 22 and the remaining refrigerant is compressed as it is and discharged to the casing 1 through the first discharge hole 22. In such a manner, the compressor is started in the middle operation mode.

Then, as shown in FIG. 10, by operating the back pressure switching unit in the opposite manner, a high-pressure refrigerant gas is supplied to the rear surface of the first compression portion 81 a of the sliding valve 81, such that the sliding valve 81 moves to the left side to allow the first compression portion 81 a to block the bypass hole 34. Thusly, every compression refrigerant within the cylinder is discharged to the casing 1 through the first discharge hole 22, so that the compressor is operated in the power operation mode.

Then, as described above, the process in which the operation mode is converted into to the middle operation mode and is converted again into the power operation mode after a certain period of time (within one minute), is repetitively performed, thereby continuing the operation of the compressor as illustrated in FIG. 11.

The operation of the air conditioner employing the capacity variable type rotary compressor in which a plurality of discharge holes are disposed at different positions, will now be described. Namely, as power is applied, the middle operation mode is carried out, in which a portion of a compression gas within the cylinder is excluded to the bypass hole 34 for a certain period of time.

Then, an indoor temperature is compared to a set temperature (A). If the indoor temperature is higher than the set temperature (A), the operation is performed in a state that the sliding valve 81 of the capacity varying unit 80 blocks the bypass hole 34, thereby performing the maximum cooling capability operation (power operation).

Then, during the maximum operation mode, the indoor temperature is compared with the set temperature (A). If the indoor temperature is lower than the set temperature (A), the middle cooling capability operation is performed, in which a portion of a compression gas is excluded by opening the bypass hole 34. Here, during the middle cooling capability operation, if the indoor temperature is lower than the set temperature (A), the indoor temperature is compared to a set temperature (B). If the indoor temperature is higher than the set temperature (B), the middle cooling capability operation is continued. However, if not, the compressor is stopped.

Then, during the middle operation mode, the indoor temperature is compared to the set temperature (B). If the indoor temperature is lower than the set temperature (B), power is turned off so as to stop the. compressor. Here, before the power operation or the middle operation is performed, the indoor temperature is compared with the set temperature (A). Then, the operation is performed upon determining the required total cooling capability of compressor according to the temperature difference, such that the cooling capability of the air conditioner can be variously controlled to thereby improve efficiency of the air conditioner and prevent unnecessary power consumption. For example, if the total cooling capability of the compressor is intended to be approximately 20%, for three minutes, the power operation is performed for a period of time as long as 0.2*time (t) and the middle operation is performed for a period of time as long as 0.8*time(t). Also, because the middle cooling capability operation is performed as the compressor is started, the compressor can be easily started with its compression load lowered, and the compressor can be operated even in a state that the pressure balance between the high-pressure side and the low-pressure side is lost, thereby shortening a time required for re-starting. Also, compressor vibration generated when the compressor is started can be reduced, and reverse-rotation of the rotary shaft which occurs due to back-flow of a compression gas can be prevented, thereby improving reliability of the compressor. In addition, according to the present embodiment, if the cooling capability of the compressor is excessive during the middle operation, the air-conditioning operation can be optimized upon frequent switching between the stopping and the middle operation.

In the capacity variable type rotary compressor in accordance with the present invention, the second discharge hole 32 may be formed a the second sub-bearing 30. However, as occasion demands, the second discharge hole 32 may be penetratingly formed from the inner circumferential surface of the cylinder 110 to its outer circumferential surface. Namely, as shown in FIG. 13, the second discharge hole 111 is formed at one side circumferential surface of the cylinder 110 to bypass a portion of a refrigerant gas. The first discharge hole (not shown) is formed at the main bearing 120 covering an upper surface of the cylinder 110, and the bypass hole is formed at the sub-bearing 130 covering a lower surface of the cylinder 110 to be in communication with the second discharge hole 111, thereby allowing the second discharge hole 111 to be in communication with the intake hole (not shown) of the cylinder 110.

Preferably, the diameter of the second discharge hole 111 or the elasticity coefficient of the second discharge valve of the one embodiment apply in this case.

Also, the discharge valve (not shown) opening and closing the first discharge hole is a lid-type valve whose one end is fixed, and the second discharge valve 112 is formed as a plate-shaped valve to be slidingly opened and closed. To this end, a special valve hole 110 a communicating with the second discharge hole 111 is penetratingly formed at the cylinder 110 in a radial direction.

As described above, a plurality of discharge holes and a plurality of discharge valves are provided and a position angle of one of them can be freely changed, such that the cooling capability in a capability-lowered mode can be arbitrarily set between 0˜100%. Accordingly, the air-conditioning operation can be performed according to various circumstances.

Also, because the operation mode is switched upon controlling a capability varying unit within a compressor having a pilot valve which is small and reliable and requires small power consumption, a place where the air conditioner employing such a compressor is installed can be in a pleasant condition, and the optimum air conditioning can be performed according to a load of a weather, thereby reducing annual power consumption.

Also, as compared to a capacity control method using an inverter, a unit cost can be greatly lowered, a system can be simplified, and reliability thereof can be improved.

The capacity variable type rotary compressor, its operation method, and an operation method of an air conditioner having the same can be used for every device which requires a compressor, such as an air conditioner, a refrigerator, a showcase or the like. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

1. A capacity variable type rotary compressor comprising: a casing that is provided with a gas intake pipe communicating with an evaporator and a gas discharge pipe communicating with a condenser; a cylinder that is fixedly installed in the casing, and includes an internal space at its center in which a rolling piston compresses a refrigerant while orbiting, an intake hole penetratingly formed at the internal space in a radial direction and communicating with the gas intake pipe, and a vane slit formed in a radial direction so as to support a vane contacting with the rolling piston in a radial direction and dividing the internal space into a compression chamber and an intake chamber; a plurality of bearing plates that form an internal space together by covering both upper and lower sides of the cylinder, discharge holes formed on the same axis, communicating with the internal space of the cylinder and discharging a compression refrigerant, and a bypass hole communicating with one discharge hole and communicating with the intake hole of the cylinder; a plurality of discharge valves that are installed at a front end surface of each discharge hole so as to open and close the discharge hole of each bearing plate; a capacity varying unit that is coupled to the bearing plate and selectively opens and closes the bypass hole of the bearing plate to exclude a portion of a compression refrigerant to the intake hole; and a back pressure switching unit that differentially supplies back pressure to the capacity varying unit so as to allow the capacity varying unit to open and close the bypass hole according to an operation mode of the compressor.
 2. A capacity variable type rotary compressor comprising: a casing that is provided with a gas intake pipe communicating with an evaporator and a gas discharge pipe communicating with a condenser; a cylinder that is fixedly installed in the casing, and includes an internal space at its center in which a rolling piston compresses a refrigerant while orbiting, an intake hole penetratingly formed at the internal space in a radial direction and communicating with the gas intake pipe, and a vane slit formed in a radial direction so as to support a vane contacting with the rolling piston in a radial direction and dividing the internal space into a compression chamber and an intake chamber; a plurality of bearing plates that form an internal space together by covering both upper and lower sides of the cylinder, discharge holes formed on different axes, communicating with the internal space of the cylinder and discharging a compression refrigerant, and a bypass hole communicating with one discharge hole and communicating with the intake hole of the cylinder; a plurality of discharge valves that are installed at a front end surface of each discharge hole so as to open and close the discharge hole of each bearing plate; a capacity varying unit that is coupled to the bearing plate and selectively opens and closes the bypass hole of the bearing plate to exclude a portion of a compression refrigerant to the intake hole; and a back pressure switching unit that differentially supplies back pressure to the capacity varying unit so as to allow the capacity varying unit to open and close the bypass hole according to an operation mode of the compressor.
 3. A capacity variable type rotary compressor comprising: a casing that is provided with a gas intake pipe communicating with an evaporator and a gas discharge pipe communicating with a condenser; a cylinder that is fixedly installed in the casing, and includes an internal space at its center in which a rolling piston compresses a refrigerant while orbiting, an intake hole penetratingly formed at the internal space in a radial direction and communicating with the gas intake pipe, and a vane slit formed in a radial direction so as to support a vane contacting with the rolling piston in a radial direction and dividing the internal space into a compression chamber and an intake chamber; a plurality of bearing plates that form an internal space together by covering both upper and lower sides of the cylinder, wherein a discharge hole communicating with the internal space of the cylinder and discharging a compression gas into the casing is formed at one bearing plate such that its axial center crosses the discharge hole of the cylinder at a right angle, a and at the other bearing plate, a bypass hole allowing the discharge hole of the cylinder to be in communication with the intake hole is formed; a plurality of discharge valves that are installed at a front end surface of each discharge hole so as to open and close the discharge hole of each bearing plate; a capacity varying unit that is coupled to the bearing plate and selectively opens and closes the bypass hole of the bearing plate to exclude a portion of a compression refrigerant to the intake hole; and a back pressure switching unit that differentially supplies back pressure to the capacity varying unit so as to allow the capacity varying unit to open and close the bypass hole according to an operation mode of the compressor.
 4. A capacity variable type rotary compressor comprising: a casing that is provided with a gas intake pipe communicating with an evaporator and a gas discharge pipe communicating with a condenser; a cylinder that is fixedly installed in the casing, and includes an internal space at its center in which a rolling piston compresses a refrigerant while orbiting, an intake hole penetratingly formed at the internal space in a radial direction and communicating with the gas intake pipe, and a vane slit formed in a radial direction so as to support a vane contacting with the rolling piston in a radial direction and dividing the internal space into a compression chamber and an intake chamber; a plurality of bearing plates that form an internal space together by covering both upper and lower sides of the cylinder, wherein a discharge hole communicating with the internal space of the cylinder and discharging a compression gas into the casing is formed at one bearing plate so as to be eccentric from the discharge hole of the cylinder, and at the other bearing plate, a bypass hole allowing the discharge hole of the cylinder to be in communication with the intake hole is formed at the other bearing plate; a plurality of discharge valves that are installed at a front end surface of each discharge hole so as to open and close the discharge hole of each bearing plate; a capacity varying unit that is coupled to the bearing plate and selectively opens and closes the bypass hole of the bearing plate to exclude a portion of a compression refrigerant to the intake hole; and a back pressure switching unit that differentially supplies back pressure to the capacity varying unit so as to allow the capacity varying unit to open and close the bypass hole according to an operation mode of the compressor.
 5. The compressor of claim 1, wherein the plurality of discharge holes are formed at the maximum compression angle.
 6. The compressor of claim 2, wherein the discharge hole communicating with the inside of the casing is formed at the maximum compression angle while the discharge hole communicating with the bypass hole is placed within a range of 170˜200 degrees from the vane in a direction that the rolling piston rotates.
 7. The compressor of claim 1, wherein the plurality of discharge holes have the same diameter.
 8. The compressor of claim 1, wherein, of the plurality of discharge holes, the discharge hole communicating with the bypass hole has a diameter that is larger than that of the other discharge hole.
 9. The compressor of claim 1, wherein the plurality of discharge holes have the same elasticity coefficient.
 10. The compressor of claim 1, wherein, of the plurality of discharge valves, the discharge valve of a discharge hole side communicating with the bypass hole has a relatively small elasticity coefficient.
 11. The compressor of claim 1, wherein the bearing plate has therein a valve hole crossing the bypass hole at a right angle, and the capacity varying unit is installed at the valve hole.
 12. The compressor of claim 11, wherein the capacity varying unit comprises: a sliding valve slidingly inserted in the valve hole and opening and closing the bypass hole by moving within the valve hole according to a pressure difference due to the back pressure switching unit; at least one valve spring elastically supporting a moving direction of the sliding valve and moving the sliding valve to a closed position when there is no pressure difference between both ends; and a valve stopper shielding the valve hole to prevent separation of the sliding valve.
 13. The compressor of claim 12, the sliding valve comprises: a plurality of compression portions placed at both sides of the bypass hole, formed to slidingly contact with an inner circumferential surface of the valve hole, and moving upon receiving pressure through the back pressure switching unit such that at least one of them can open and close the bypass hole; and a communication portion connecting the plurality of pressure portions and having a gas passing path formed between its outer circumferential surface and the valve hole.
 14. The compressor of claim 13, wherein the valve spring is installed to allow one pressure portion to block the bypass hole when pressures are the same on both ends of the sliding valve.
 15. The compressor of claim 12, wherein the valve spring is installed to allow the communication portion to communicate with the bypass hole and thusly open the bypass hole when pressures are the same on both ends of the sliding valve.
 16. The compressor of claim 1, wherein a spring fixing groove to which the elastic member is insertedly fixed is formed at the pressure portion of the sliding valve.
 17. The compressor of claim 11, wherein the valve hole includes a first back pressure hole and a second back pressure hole which respectively communicate with an outlet of the back pressure switching unit.
 18. The compressor of claim 1, wherein the back pressure switching unit comprises: a pressure switching valve assembly communicating with the gas intake pipe and the gas discharge pipe and allowing the gas intake pipe and the gas discharge pipe to be alternately connected to both sides of the capacity varying unit; a first connection “pipe connecting a first outlet of the pressure switching valve assembly to one side of the capacity varying unit; and a second connection pipe connecting a second outlet of the pressure switching valve assembly to the other side of the capacity varying unit.
 19. The compressor of claim 17, wherein the switching valve assembly comprises: a switching valve housing having a low-pressure side inlet connected to the gas intake pipe, a high-pressure side inlet connected to the gas discharge pipe, a first outlet connected to the first connection pipe and a second outlet connected to the second connection pipe; a switching valve slidingly coupled to the inside of the switching valve housing and selectively allowing connection between the low-pressure side inlet and the first outlet and between the high-pressure side inlet and the second outlet or between the low-pressure side inlet and the second outlet and between the high-pressure side inlet and the first outlet; an electromagnet installed at one side of the switching valve housing and moving the switching valve by applied power; and an elastic member restoring the switching valve when power being applied to the electromagnet is cut off.
 20. An operation method of a capacity variable type rotary compressor of claim 1, alternately performing: a power operation mode in which the operation is performed with the maximum cooling capability as a capacity varying unit blocks a bypass hole when the compressor is started; and a saving operation mode in which, during the power operation mode, if the cooling capability needs to be lowered upon calculating the proper cooling capability of the compressor by a control unit, the back pressure switching unit is operated such that the capacity varying unit opens the bypass hole to allow all of the compression refrigerant within a cylinder to be excluded to an intake hole.
 21. The method of claim 20, wherein the saving operation mode is continued or discontinued upon detecting whether there is a pressure difference between a high pressure side and a low pressure side.
 22. The method of claim 21, wherein if temperatures of a condenser and an evaporator are within a preset temperature range upon detecting those temperatures, the saving operation is extended upon determining that the pressure difference between the high pressure side and the low pressure side is an effective pressure difference, while if the detected temperatures are not within the preset temperature range, the back pressure switching unit is operated so as to directly perform conversion into the power operation mode.
 23. An operation method of a capacity, variable type rotary compressor of claim 2, alternately performing: a middle operation mode in which a capacity varying unit opens a bypass hole when the compressor is started so as to allow a portion of a compression refrigerant of a cylinder to be excluded to an intake hole; a power operation mode in which the operation is performed with the maximum cooling capability as the capacity varying unit blocks the bypass hole upon operating a back pressure switching unit after the middle operation mode is performed for a certain period of time; and a middle operation mode in which, during the power operation mode, if the cooling capability needs to be lowered upon calculating the proper cooling capability of the compressor by a control unit, the back pressure switching unit is operated in the opposite manner such that the capacity varying unit opens the bypass hole to allow a portion of the compression refrigerant of the cylinder to be excluded to the intake hole.
 24. The method of claim 23, wherein the middle operation mode is continued or discontinued upon detecting whether there is a pressure difference between a high pressure side and a low pressure side.
 25. The method of claim 24, wherein if temperatures of a condenser and an evaporator are within a preset temperature range upon detecting those temperatures, the saving operation is extended upon determining that the pressure difference between the high-pressure side and the low-pressure side is an effective pressure difference, and, while if the detected temperatures are not within the preset temperature range, the back pressure switching unit is operated so as to directly perform conversion into the power operation mode.
 26. The method of claim 23, wherein, during the middle operation mode, if the cooling capability needs to be lowered to zero upon calculating the proper cooling capability by a control unit, a stopping mode in which the compressor is stopped by turning OFF power is further performed.
 27. An operation method of an air conditioner having a capacity variable type rotary compressor of claim 1, performing: a maximum cooling capability mode in which, if an indoor temperature is higher than a set temperature (A) upon comparing the indoor temperature to the set temperature (A) with power supplied, the operation is performed with the maximum cooling capability as a capacity varying unit of a compressor blocks a bypass hole communicating with an indoor space of a cylinder; a minimum cooling capability mode in which, during the maximum cooling capability mode, if the indoor temperature is lower than the set temperature (A) upon comparing the indoor temperature with the set temperature (A), the capacity varying unit opens the bypass hole to allow all of the compression refrigerant of the internal space of the cylinder to be excluded to an intake hole, wherein if the indoor temperature is higher than the set temperature (A), the maximum cooling capability mode is continuously performed; and a stopping mode in which, during the minimum cooling capability mode, if the indoor temperature is lower then a set temperature (B) upon comparing the indoor temperature with the set temperature (B), the compressor is stopped by turning OFF power.
 28. An operation method of an air conditioner having a capacity variable type rotary compressor of claim 1, performing: a middle cooling capability mode in which, if an indoor temperature is higher than a set temperature (A) upon comparing the indoor temperature with the set temperature (A) with power supplied, a capacity varying unit of a compressor opens a bypass hole communicating with an internal space of a cylinder to allow a portion of a compression refrigerant within a cylinder to be excluded to an intake hole; a maximum cooling capability mode in which, during the middle cooling capability mode, if the indoor temperature is higher than the set temperature (A) upon comparing the indoor temperature with the set temperature (A), the operation is performed with the maximum cooling capability as the capacity varying unit blocks the bypass hole communicating with the internal space of the cylinder; a middle cooling capability mode in which, during the maximum cooling capability mode, if the indoor temperature is lower than the set temperature (A) upon comparing the indoor temperature with the set temperature (A), the bypass hole is opened to allow a portion of a compression gas to be excluded; and a stopping mode in which, during the middle cooling capability mode, if the indoor temperature is lower than a set temperature (B) upon comparing the indoor temperature with the set temperature (B), the compressor is stopped by turning OFF the power.
 29. The method of claim 27, wherein a total cooling capability determination step of determining a total cooling capability of the compressor required for mode conversion and an operation time of each mode is previously performed. 